#define ONE_ANSWER 1

int n, d[500][500];
int nf, f[100];
int fd[500];

main() {
	int i, j, k, x, y, z, min, nmin;

	scanf( " %d %d", &nf, &n );
	for( i = 0; i < nf; i++ ) {
		scanf( " %d", &f[i] );
		f[i]--;
	}
	for( i = 0; i < n; i++ ) for( j = 0; j < n; j++ ) d[i][j] = 1000000000;
	for( i = 0; i < n; i++ ) d[i][i] = 0;
	while( scanf( " %d %d %d", &x, &y, &z ) == 3 ) {
		x--; y--;
		d[x][y] = d[y][x] = z;
	}
	for( i = 0; i < n; i++ ) for( j = 0; j < n; j++ ) for( k = 0; k < n; k++ ) {
		x = d[j][i] + d[i][k];
		if( d[j][k] > x ) d[j][k] = x;
	}
	for( i = 0; i < n; i++ ) {
		fd[i] = 1000000000;
		for( j = 0; j < nf; j++ )
			if( d[i][f[j]] < fd[i] ) fd[i] = d[i][f[j]];
	}
	nmin = -1; min = 1000000000;
	for( i = 0; i < n; i++ ) {
		x = -1;
		for( j = 0; j < n; j++ ) {
			y = (d[j][i]<fd[j]) ? d[j][i] : fd[j];
			if( y > x ) x = y;
		}
		if( x < min ) {
			nmin = i; 
			min = x;
		}
	}
#if !ONE_ANSWER
	printf( "Possible answers:" );
	for( i = 0; i < n; i++ ) {
		x = -1;
		for( j = 0; j < n; j++ ) {
			y = (d[j][i]<fd[j]) ? d[j][i] : fd[j];
			if( y > x ) x = y;
		}
		if( x == min ) printf( " %d", i+1 );
	}
	putchar( '\n' );
#else
	printf( "%d\n", nmin+1 );
#endif
}